Method and apparatus for selecting a multi-band access point to associate with a multi-band mobile station

CROSS REFERENCE TO RELATED APPLICATION

0001This application claims the benefit of U.S. application Ser. No. 11/284,242 filed on Nov. 21, 2005, which claims priority to U.S. Provisional Patent Application No. 60/667,523 filed Apr. 1, 2005, which is incorporated by reference as if fully set forth.

FIELD OF INVENTION

0002The present invention relates to a wireless communication system including a plurality of multi-band access points (APs) and a multi-band wireless transmit/receive unit (WTRU), (i.e., a mobile station). More particularly, the present invention is related to a method and apparatus for selecting a particular one of the multi-band APs to associate with based on frequency band information transmitted from the multi-band APs to the multi-band WTRU.

BACKGROUND

0003A typical wireless local area network (WLAN) includes an AP which provides radio access to WTRUs in a coverage area of the AP. The AP is comprised by a basic service set (BSS) which is a basic building block of an IEEE 802.11-based WLAN. Multiple BSSs may be interconnected through a distribution system (DS) to form an extended service set (ESS).

0004The WLAN may be configured in an infrastructure mode or an Ad-hoc mode. In the infrastructure mode, wireless communications are controlled by an AP. The AP periodically broadcasts beacon frames to enable WTRUs to identify, and communicate with, the AP. In the Ad-hoc mode, a plurality of WTRUs operate in a peer-to-peer communication mode. The WTRUs establish communication among themselves without the need of coordinating with a network element. However, an AP may be configured to act as a bridge or router to another network, such as the Internet.

0005The WTRUs and the AP may be configured to utilize multiple frequency bands for communication. In a conventional wireless communication system, a multi-band WTRU transmits multiple probe requests on different channels of a frequency band to discover if there are any APs available in the area. Once an AP receives the probe request, it sends a probe response packet to the WTRU. The AP will send the probe response packet on its operating channel in a particular frequency band. The probe response packet contains required parameters, such as supported rate, or the like, for the WTRU to associate with the AP. The WTRU will send an association request packet and waits for an association response packet from an AP for further data communication.

0006Once associated, the multi-band WTRU may scan other frequency bands in search of a better communication band by transmitting a probe request packet and waiting for a probe response packet. Upon receiving another probe response packet, the WTRU compares the frequency bands and/or the AP and selects a more preferable frequency band and/or AP.

0007In the conventional wireless communication system, the multi-band WTRU must scan and compare different frequency bands to determine the frequency band that provides the best quality of wireless communications. However, these scanning and comparison functions are time-consuming and require a significant amount of battery power. A method and apparatus for reducing the amount of time and battery power required to make frequency band and channel selection decisions is desired.

SUMMARY

0008The present invention is related to a method and apparatus for selecting one of a plurality of multi-band APs to associate with a multi-band WTRU. The multi-band APs broadcast frequency band information regarding multiple frequency bands on which the multi-band AP is configured to operate. The multi-band WTRU selects a particular multi-band AP to associate with and a frequency band to use to communicate with the selected multi-band AP based on the frequency band information. If the multi-band WTRU receives frequency band information from the selected multi-band AP which indicates that a characteristic, (e.g., throughput, path loss, load, capacity, backhaul), of the selected frequency band is unacceptable, the multi-band WTRU determines whether to disassociate with the selected multi-band AP or to continue to associate with the selected multi-band AP via a different frequency band.

BRIEF DESCRIPTION OF THE DRAWINGS

0009A more detailed understanding of the invention may be had from the following description, given by way of example and to be understood in conjunction with the accompanying drawings wherein:

0010<figref idref="DRAWINGS">FIG. 1</figref> shows a wireless communication system including a plurality of multi-band APs and a multi-band WTRU which operate in accordance with the present invention;

0011<figref idref="DRAWINGS">FIG. 2</figref> is an exemplary beacon frame which comprises frequency band information transmitted from the multi-band APs to the multi-band WTRU of the wireless communication system of <figref idref="DRAWINGS">FIG. 1</figref>;

0012<figref idref="DRAWINGS">FIG. 3</figref> is a flow diagram of a process for the multi-band WTRU to select one of the multi-band APs to associate with in accordance with the present invention;

0013<figref idref="DRAWINGS">FIG. 4</figref> is a flow diagram of a process for the multi-band WTRU to determine whether to change a particular frequency band used for wireless communications with a multi-band AP or to associate with a different multi-band AP in accordance with the present invention; and

0014<figref idref="DRAWINGS">FIG. 5</figref> is a flow diagram of a process for establishing a wireless communication link between the multi-band WTRU and a preferable multi-band AP over a preferable frequency band in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

0015Hereafter, the terminology “WTRU” includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. Such WTRUs include, but are not limited to, phones, video phones, and Internet ready phones, personal data assistances (PDAs) and notebook computers with wireless modems that have network capabilities.

0016When referred to hereafter, the terminology “AP” includes but is not limited to a Node-B, a base station, a site controller or any other type of interfacing device in a wireless environment that provides other WTRUs with wireless access to a network with which the AP is associated.

0017The features and elements of the present invention may be implemented on a single IC, (such as an application specific integrated circuit (ASIC)), multiple ICs, discrete components or a combination of discrete components and ICs.

0018The present invention is applicable to any type of wireless communication systems including, but not limited to, 802.x-based wireless communication systems.

0019<figref idref="DRAWINGS">FIG. 1</figref> shows a wireless communication system <b>100</b> including a plurality of multi-band APs <b>105</b>₁-<b>105</b>_Nand a multi-band WTRU <b>110</b> which operate in accordance with the present invention. Each of the multi-band APs <b>105</b>₁-<b>105</b>_Nand the multi-band WTRU <b>110</b> operate on at least two frequency bands. The multi-band APs <b>105</b>₁-<b>105</b>_Ntransmit frequency band information <b>115</b>₁-<b>115</b>_Nwhich indicates the different multi-bands that the respective APs <b>105</b>₁-<b>105</b>_Nare configured to operate on. Each of the multi-band APs <b>105</b>₁-<b>105</b>_Ninclude a respective transceiver <b>120</b>₁-<b>120</b>_Nand a respective processor <b>125</b>₁-<b>125</b>_N. Each respective transceiver <b>120</b>₁-<b>120</b>_Nis configured to operate on at least two different frequency bands. Each respective processor <b>125</b>₁-<b>125</b>_Ngenerates and formats the respective frequency band information <b>115</b>₁-<b>115</b>_Nand provides it to the transceiver <b>120</b>₁-<b>120</b>_Nfor transmission. The multi-band WTRU <b>110</b> also includes a transceiver <b>130</b> and a processor <b>135</b>. The transceiver <b>130</b> is configured to operate on at least two different frequency bands. The processor <b>135</b> processes the frequency band information <b>115</b>₁-<b>115</b>_Nreceived by the transceiver <b>130</b> from the multi-band APs <b>105</b>₁-<b>105</b>_N, selects a multi-band AP <b>105</b> to associate with, and a frequency band to use in communication with the selected multi-band AP <b>105</b>, based on the frequency band information <b>115</b>₁-<b>115</b>_N.

0020The multi-band WTRU <b>110</b> and the multi-band APs <b>105</b>₁-<b>105</b>_Nmay use any management, control or data packet to provide the frequency band information to the multi-band WTRU <b>110</b>. For example, an authentication frame, (which is a management frame), can also be used to send multi-band frequency information. Similarly, this packet can be piggybacked on any of the current or future WLAN packets.

0021Alternatively, a proprietary message exchange between the multi-band WTRU <b>110</b> and the multi-band APs <b>105</b>₁-<b>105</b>_Nmay also be utilized to provide the frequency band information to the multi-band WTRU <b>110</b>.

0022<figref idref="DRAWINGS">FIG. 2</figref> shows an exemplary beacon frame which comprises frequency band information <b>115</b> transmitted from each of the multi-band APs <b>105</b>₁-<b>105</b>_Nto the multi-band WTRU <b>110</b> of the wireless communication system <b>100</b> of <figref idref="DRAWINGS">FIG. 1</figref>. The frequency band information <b>115</b> indicates whether a particular multi-band AP <b>105</b> supports multiple frequency bands <b>205</b>₁-<b>205</b>_N, channel numbers <b>215</b> and timing information <b>220</b> or the like.

0023The frequency band information <b>115</b> may further include quality metric information <b>210</b>₁-<b>210</b>_Nfor each of the frequency bands <b>205</b>₁-<b>205</b>_N. The quality metric information may include, but is not limited to, path loss, load, (e.g., the number of associated WTRUs <b>110</b>), throughput, capacity and backhaul on each frequency band.

0024<figref idref="DRAWINGS">FIG. 3</figref> is a flow diagram of a process <b>300</b> for establishing a wireless communication link between a particular one of <b>115</b>₁-<b>115</b>_Nand the multi-band WTRU <b>110</b> in the wireless communication system <b>100</b> of <figref idref="DRAWINGS">FIG. 1</figref> based on frequency band information <b>115</b>₁-<b>115</b>_Ntransmitted from the multi-band APs <b>105</b>₁-<b>105</b>_Nto the multi-band WTRU <b>110</b>. In step <b>305</b>, a plurality of multi-band APs <b>105</b>₁-<b>105</b>_Nbroadcast frequency band information <b>115</b>₁-<b>115</b>_Nregarding multiple frequency bands on which the respective multi-band APs <b>105</b>₁-<b>105</b>_Nare configured to operate. The frequency band information <b>115</b>₁-<b>115</b>_Nmay be broadcast in a beacon frame, as shown in <figref idref="DRAWINGS">FIG. 2</figref>. In step <b>310</b>, a multi-band WTRU <b>110</b> receives and processes the frequency band information <b>115</b>₁-<b>115</b>_N. In step <b>315</b>, the multi-band WTRU <b>110</b> selects a particular one of the multi-band APs <b>105</b>₁-<b>105</b>_Nto associate with, and a frequency band to use to communicate with the selected multi-band AP <b>105</b> based on the frequency band information <b>115</b>₁-<b>115</b>_N.

0025<figref idref="DRAWINGS">FIG. 4</figref> is a flow diagram of a process <b>400</b> for the multi-band WTRU <b>110</b> to determine whether to change a particular frequency band used for wireless communications with a multi-band AP <b>105</b>, or to associate with a different multi-band AP <b>105</b> in accordance with the present invention. In step <b>405</b>, the multi-band WTRU <b>110</b> associates with a particular multi-band AP <b>105</b> on a particular frequency band. In step <b>410</b>, the multi-band WTRU <b>110</b> receives frequency band information <b>115</b> from the particular multi-band AP <b>105</b> including a quality metric which indicates that the particular frequency band has, for example, poor throughput. In step <b>415</b>, the multi-band WTRU <b>110</b> either disassociates with that the multi-band AP <b>105</b> and associates with another multi-band AP <b>105</b> continues to associate with the same multi-band AP <b>105</b> over a different frequency band for which the frequency band information <b>115</b> includes a quality metric which indicates a good, (i.e., high), throughput.

0026<figref idref="DRAWINGS">FIG. 5</figref> is a flow diagram of a process <b>500</b> for establishing a wireless communication link between the multi-band WTRU and a preferable multi-band AP over a preferable frequency band in accordance with the present invention. In step <b>505</b>, a multi-band WTRU <b>110</b> broadcasts an association request packet or a probe request packet which is received by a plurality of multi-band APs <b>105</b>₁-<b>105</b>_N. The multi-band WTRU <b>110</b> may include an indication of the multi-band capability and related information of the WTRU <b>110</b> in the request packet. In step <b>510</b>, each of the multi-band APs <b>105</b>₁-<b>105</b>_Nsends an association response packet or a probe response packet to the multi-band WTRU <b>110</b> which includes frequency band information <b>115</b>₁-<b>115</b>_Nin accordance with the multi-band capability of the WTRU <b>110</b>. In step <b>515</b>, the multi-band WTRU <b>110</b> selects a preferable frequency band and a preferable multi-band AP <b>105</b> to associate with based on the frequency band information <b>115</b>₁-<b>115</b>_N.

0027In another embodiment, the wireless communication system <b>100</b> may also include a single-band AP and a single-band WTRU, in addition to the multi-band APs <b>105</b>₁-<b>105</b>_Nand the multi-band WTRU <b>104</b><i>a</i>. If a single-band WTRU is associated with a multi-band AP <b>105</b>, the information regarding the multiple frequency bands of the multi-band AP <b>105</b> other than information regarding the frequency band on which the single-band WTRU is configured to operate will be simply ignored by the single-band WTRU since the single-band WTRU not configured to communicate on multiple frequency bands. The single-band AP broadcasts its information regarding its single frequency band, (such as timing, load, or the like) in a beacon frame. Both a single-band WTRU and a multi-band WTRU <b>110</b> may utilize this information to decide whether or not to associate with the single-band AP.

0028In accordance with the present invention, the multi-band WTRU <b>110</b> is not required to consume significant time and battery power for scanning various frequency bands in search of an adequate AP to associate with. Moreover, by providing the multi-band WTRU <b>110</b> with quality metrics of each frequency band, (such as throughput), the WTRU is enabled to optimize not only its own throughput, but also the throughput of the AP <b>105</b>.

0029Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention.